Manifestation of LO-LA phonons in Raman scattering in graphene

We analyze the spectral density of Raman scattering in graphene accompanied by the emission of a pair of LO or LA phonons from the corner of the Brillouin zone. Using a minimal tight-binding model approach, we find that the lineshape of the corresponding Raman signal consists of two peaks with a strongly non-Lorentzian (almost triangular) form with their width and the splitting between the peaks being strongly dependent on the energy of the incoming photon. The asymmetric lineshape is determined by the kinematics of the fully-resonant two-phonon process, and it reflects a strong anisotropy of LO-LA phonons' dispersion around the Brillouin zone corners. (C) 2011 Elsevier Ltd. All rights reserved.